1. Field of the Invention
The invention concerns a method of fixing a polarization-preserving optical fiber and a ferrule for a fiber of this kind.
2. Description of the Prior Art
Polarization-preserving optical fibers include internal components whereby they impose or at least preserve a linear polarization of the light that they guide. The plane defined by the axis of the fiber and this polarization is referred to hereinafter as the "polarization-preserving plane". These fibers are conventionally used in telecommunication systems when light received by an optical component must have a correct plane of polarization as defined by the component. To this end the light is guided to the component by a fiber of this kind.
The fixing of the fiber must then not only ensure alignment and correct longitudinal and transverse positioning of the end of the fiber relative to the component, but also coincidence of the polarization-preserving plane of the fiber and the polarization-plane defined by the component. To this end an operation is carried out to orient the polarization-preserving plane. It is difficult because the internal components of the fiber are all transparent, and so the direction of this plane cannot be determined merely by visual examination of the fiber.
In the usual case of a fiber imposing a linear polarization, unpolarized light has previously been injected into the fiber and the direction of the plane of polarization of the light leaving the end of the fiber determined. The fiber is then rotated about its axis to move this plane into the direction required for the polarization-preserving plane.
The optical fiber may be held in the conventional way in a capillary passage formed in a ceramic ferrule.
One object of the present invention is to simplify the operation of orienting the polarization-preserving plane of an optical fiber to be coupled to an optical component sensitive to that orientation.